1. Field of the Invention
The present invention relates to a non-halogen flame-retardant insulated electric wire and a non-halogen flame-retardant cable.
2. Description of the Related Art
Electric wires and cables used in rolling stock, automobiles, devices, etc., desirably have high abrasion resistance, flame retardancy, good low-temperature characteristics, and other properties as occasion demands.
Polyvinyl chloride (PVC), which is inexpensive and highly flame retardant, has been widely used as the electric wire coating material. However, PVC contains halogen and releases halogen gas when burned, raising environmental issues. Thus, non-halogen electric wire coating materials have been sought after.
One approach to obtaining a non-halogen flame retardant electric wire known in the art is to load the coating material with a metal hydroxide, such as magnesium hydroxide or aluminum hydroxide, that acts as a flame retardant. In order to load the coating material with such a flame retardant, a soft polyolefin, such as an ethylene-vinyl acetate copolymer (EVA) or an ethylene-acrylic acid ester copolymer, is used as a base polymer of a coating material (refer to Japanese Unexamined Patent Application Publication No. 2006-8873).
However, soft polyolefins such as EVA have low strength, deform easily, are susceptible to abrasion, and are easily damaged.
Moreover, in stripping an electric wire terminal by using a wire stripper or the like, the coating material may become stretched and a clean cut may not be obtained, thereby leaving some part of the coating material on a conductor in some instances. When this happens, sparks occur during resistance welding and render the process difficult to perform.
Moreover, electric wires may fuse to each other or deform in a high-temperature environment involving a temperature higher than the melting point of the coating material. This makes inspection of wiring and replacement operation difficult.